In my case it was the same problem. As a workaround I modified the version of my owncloud virtually to 9.1.5.2. This can be done by modifying the file config/config.php in your owncloud installation directory (modify the string ‘version’ => ‘9.1.6.2’ to ‘version’ => ‘9.1.5.2’). After this you are able to manually install nextcloud (haven’t tried this with the installer method).